Stations allow you to use a route that is 'potentially claimed by another player'. It does not count, unless there is another player on the route. Please fix app or rulebook to reflect this.

Check page 6 of the Ticket to Ride: Europe rule book. It says,

"A Train Station allows its owner to use one, and only one, of the routes belonging
to another player, into (or out of) that city to help him connect the cities on his
Destination Tickets. "

Notice that it says, belonging to another player...so it is useless until another player has a track going into (or out of) the city. You can still build it, but nothing will happen because there is no trains to borrow.

"Potentially claimed by another player" means that a station in theory would work via your own trains, even though the station would be completely redundant. It's a bad phrasing, but it's not incorrect.